*john ludley asked the Naked Scientists:*

I am trying to calculate the volume of the universe, but have a problem. Although we can calculate the volume of, say, a house in cubic metres, I am stumped by the 4-dimensional aspects of the universe.

We believe that the farthest distance between any two points in the universe is 13.5 B light years. But using the balloon analogy, this isn't the radius of the universe. In fact continuing the analogy, the farthest distance between two points on a balloon (call it *F*) is* Î .R* where* R* is the radius through the balloon, and the area of the balloon is* 4.Î .R2* , or expressing *R* in terms of* F, ** 4.F2/ Î . * Can we extend the analogy into a 3-D space and say the volume of the universe is * 4/3.Î .R3* , which using the same relationship between* F* and* R* gives* 4/3. F3/Î 2 * . I doubt it is that simple.

So what is the volume of the universe?

John Ludley

*What do you think?*